Tricarboxylic acid-functional monomers and polymers prepared from same

ABSTRACT

An unsaturated acid-functional monomer having the structure: ##STR1## wherein R 1  is hydrogen or methyl and Z is a direct bond or is a divalent radial having 1 to about 20 carbon atoms.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention involves novel polymerizable monomers having pendentcarboxylic acid groups and polymers prepared from those monomers. Themonomers have the structure: ##STR2## wherein R¹ is hydrogen or methyland Z is a direct bond or is a divalent alkyl radical having 1 to about20 carbon atoms. Preferred divalent alkyl radicals are methylene chains--(--CH₂ --)_(n) -- wherein n is 1 to 20.

This invention also relates to acid-functional polymers obtained bypolymerizing, under free radical addition polymerization conditions, (i)the unsaturated acid monomer of this invention; and (ii) optionally, atleast one other unsaturated monomer copolymerizable with the unsaturatedacid monomer. The acid-functional polymers can be neutralized to providewater-reducible polymers and/or they may be utilized as corrosion orscale inhibitors, thickeners, dispersants and as reactive agents and/orcrosslinking agents for compounds having functional groups, such asepoxy, hydroxyl or amine groups, which are reactive with acid groups.The acid-functional polymers can, therefore, be utilized in a variety ofmaterials such as plastics, fibers, adhesives, paper sizing, inks and,particularly, coating compositions.

This invention also relates to novel reactive compositions which utilizethe acid-functional polymer in combination with one or more othermaterials which can react with acid groups. These reactive compositionscan be reacted at room temperature or force dried at temperaturesranging up to about 350° F. or higher if desired. When utilized asreactive crosslinking agents for coatings, the acid-functional polymersmay be utilized in a variety of coating applications, including primersand topcoats as well as clearcoats and/or basecoats inclearcoat/basecoat compositions.

The reactive compositions typically involve the combination of theacid-functional polymer with an epoxy-functional compound. The reactivecomposition may, optionally, also incorporate an anhydride-functionalcompound and, optionally, also a hydroxyl-functional compound. All ofthese combinations can provide fast reacting, durable coatings which mayminimize the toxicity problems which may be associated with other lowtemperature curing systems.

2. Description of the Prior Art

Unsaturated, polymerizable acids, such as maleic acid, acrylic acid,methacrylic acid and polymers or copolymers incorporating thesematerials are known in the art. By the selection of one or more of theseacids, polymers may be tailored to provide a desired acid value,reactivity or other desired property. The prior art has not, however,taught polymers obtained by the polymerization of the novelstyrene-based tricarboxylic acid monomers of this invention.

Coating compositions comprising reactive combinations ofepoxy-containing compounds and compounds having acid functionality areknown in the art. For example, U.S. Pat. No. 4,859,758 teaches anacid-functional cellulose ester based polymer which could be used incombination with a polyepoxide, and optionally, a polyanhydride and,optionally a hydroxy-functional compound. Similarly, coatingcompositions comprising cyclic anhydrides and hydroxy-functionalcompounds are also known in the art. The prior art has not, however,taught the novel acid-functional polymers of this invention nor has ittaught coating compositions comprising these acid-functional polymerswith epoxy-functional compounds and, optionally, anhydride-functionalcompounds, and, optionally, hydroxy-functional compounds to provide lowtemperature curing coatings having excellent durability and performance.

BRIEF SUMMARY OF THE INVENTION

This invention involves unsaturated styrene-based monomers havingmultiple, pendent acid functionality. The monomers are useful, forexample, as neutralizing agents, thickeners, reactive diluents or theycan be polymerized to provide acid-functional polymers. These versatilemonomers also have a variety of potential applications due to theirunique combination of reactive sites. The monomers possess both multipleacid group functionality and also polymerizable unsaturationfunctionality. Either type of functionality may be reacted firstfollowed, if desired, by subsequent reaction of the other functionality.For example, one or more of the pendent acid groups on the monomer couldbe reacted with epoxy groups on an epoxide or polyepoxide to provide ahydroxy-functional product having one or more pendent, polymerizableunsaturation sites. Such a product could be subsequently polymerized,either with or without additional copolymerizable monomers such asstyrene or (meth)acrylic monomers, by peroxide initiation or by exposureto high energy radiation such as electron beam or ultraviolet light.

A particularly preferred use for the monomers of this invention involvestheir use in polymers derived by polymerizing the acid monomer throughits unsaturation either as a homopolymer or, preferably, in combinationwith one or more additional copolymerizable monomers. Theacid-functional monomers of this invention can be utilized to providereactivity, water reducibility or other performance property to acopolymer by incorporating these novel monomers into the polymerbackbone by free radical polymerization. Furthermore, since theunsaturated acids of this invention are styrene-based materials, theirreactivity ratios with other polymerizable monomers such as styrene andacrylate or methacrylate monomers under free radical polymerizationconditions will be different than the reactivity ratios of the prior artacrylic, methacrylic or maleic acids with those same copolymerizablemonomers. Therefore, the monomers of this invention can provide a way toincorporate acid side chains while altering the arrangement of othermonomers along the polymeric backbone compared to the use of the commonprior art unsaturated acids. Additionally, since the acid groups of themonomer can be, if desired, condensed to form an anhydride group, eitherbefore or after polymerization to produce anhydride-functional monomersand/or polymers, the acid monomers of this invention have specialutility when utilized as precursors for those anhydride-functionalmaterials.

This invention also relates to curable coating compositions comprisingan acid-functional polymer and an epoxy-functional compound, optionallyalso in combination with other reactive materials such as ananhydride-functional compound. If desired, in addition to theanhydridefunctional compound, hydroxy-functional compounds reactive withthe anhydrides can be added as well. The term "compound" is used in itsbroadest sense to include monomers, oligomers and polymers. Thisinvention also relates to substrates coated with the coatingcompositions of this invention.

In the most preferred coating formulations the epoxy- functionalcompound is a polyepoxide having an average of at least two epoxygroups, especially cycloaliphatic epoxy groups, per molecule.

Although the curable compositions of this invention can be utilizedwithout solvent in many applications, it is frequently preferred toutilize them in combination with about 5 to about 50% by weight of thetotal coating composition of an inert solvent. It is convenient toprovide the coating composition as a multicomponent system which isreactive upon mixing the components. Especially preferred is atwo-component system wherein the acid-functional polymer, and, ifutilized, the anhydride-functional compound are combined in one packageand the epoxy-functional compound and, if utilized, thehydroxy-functional compound provide a second package. The two packagescan then be mixed together to provide the curable coatings immediatelyprior to application.

In one preferred application, this invention relates to coatedsubstrates having a multilayer decorative and/or protective coatingwhich comprises:

(a) a basecoat comprising a pigmented film-forming polymer; and

(b) a transparent clearcoat comprising a film-forming polymer applied tothe surface of the basecoat composition;

wherein the clearcoat and/or the basecoat comprises the curable coatingcompositions of this invention. The term "film-forming polymer" meansany polymeric material which can form a film from evaporation of anycarrier or solvent.

Accordingly, one object of this invention is to provide novelunsaturated acid-functional monomers and polymers therefrom. Anotherobject is to provide improved curable compositions having excellentreactivity at low temperatures. It is a further object to providecoating compositions which may be utilized as primers, topcoats orclearcoats and/or basecoats in clearcoat/basecoat compositions. Anotherobject is to provide unsaturated acid-functional monomers which arereadily converted to anhydride-functional monomers. Another object is toprovide an improved two-component coating compositions wherein onepackage comprises an acid-functional polymer and, optionally, ananhydride-functional polymer and the other package comprises anepoxy-functional compound and, optionally, a hydroxy-functionalcompound. These and other objects will be apparent from the followingdiscussions.

DETAILED DESCRIPTION OF THE INVENTION 1. TRICARBOXYLIC ACID MONOMER

The unsaturated styrene based tricarboxylic acid monomers of thisinvention can be conveniently prepared by the reaction of the anion of atrialkyl-1,1,2-ethanetricarboxylate (such astriethyl-1,1,2-ethanetricarboxylate), with a vinyl benzene alkyl halide(such as vinyl benzyl chloride), followed by hydrolysis of the estergroups to acid groups. The vinyl benzene alkyl halide has the generalstructure: ##STR3## wherein R¹ and Z are as defined above and X is ahalogen atom. The vinyl benzene alkyl halides of various lengths of Zcan be readily prepared by a variety of methods known in the art. Forexample, Grignard reaction synthesis of the vinyl benzene alkyl halidesare representatively set forth in M. L. Hallensleben, Angew. Makronol.Chem., 31, 147 (1973), and Montheard, et al. J. Polym. Sci. Part A.,Polym. Chem., 27 (8), 2539 (1989). For cost and availability of startingmaterials, it is especially preferred that Z be a direct bond or belower alkyl of 1 to about 4 carbons. Vinyl benzyl chloride, where Z is adirect bond, R¹ is hydrogen, and X is chlorine, is especially preferred.

The reaction to produce the preferred acid-functional monomer isrepresentatively shown below wherein thetrialkyl-1,1,2-ethane-tricarboxylate istriethyl-1,1,2-ethanetricarboxylate and the vinyl benzene alkyl halideis vinyl benzyl chloride: ##STR4##

The preparation of the anion of the trialkyl-1,1,2-ethanetricarboxylateis conveniently accomplished by mixing ethanolic sodium ethoxide withthe tricarboxylate and refluxing the solution for five to ten-minutes.Typically the sodium ethoxide will be present at a level to provideabout 0.8 to about 1.1 moles of sodium ethoxide for each mole oftricarboxylate. The anion of the tricarboxylate can then be reacted withthe vinyl benzene alkyl halide by mixing the two materials in anapproximately 1 to 1 mole ratio and by maintaining the reaction atreflux, in the presence of small amounts (e.g. 500 ppm of the totalreaction mixture) of polymerization inhibitors, for 1 to about 3 hoursto prepare the vinyl benzene alkyl-1,1,2-ethane tricarboxylate. Thistricarboxylate material, in turn, can be hydrolyzed to produce thecorresponding tricarboxylic acid by reaction with base, such as sodiumhydroxide or potassium hydroxide followed by acidification.Alternatively, the hydrolysis can be conducted by direct reaction of thetricarboxylate with aqueous acid such as aqueous hydrochloric acid. Basehydrolysis is generally preferred and can be readily conducted byadmixing an aqueous and/or ethanolic solution of sodium hydroxide orpotassium hydroxide and maintaining the reaction mixture at reflux untilthe reaction is complete (typically 3 to 5 hours). The salt product canbe collected by filtration and the tricarboxylic acid is then generatedby acidifying an aqueous solution of the salt to a Ph less than about 3,typically by using dilute acid such as aqueous hydrochloric acid.

In one use of the tricarboxylic acid monomer, the monomer can beconverted to a carboxylic anhydride monomer by one of severalmechanisms. In one approach (Route B) the tricarboxylic acid monomer canbe converted first to the diacid by heating the tricarboxylic acidmonomer at temperatures over 100° C., typically 115°-140° C., until CO₂evolution ceases. If it is desired to convert the diacid to thecorresponding dicarboxylic acid anhydride, the diacid is then reactedwith at least an equimolar amount of a reactant, normally a carboxylicacid derivative such as an anhydride or acid chloride, which willproduce a better leaving group than the carboxylic acid OH. For example,the dicarboxylic acid can be reacted with acetic anhydride followed bysubsequent elimination of acetic acid upon ring closure. Acetylchloride, and especially acetic anhydride, are preferred as thecarboxylic acid derivatives.

The diacid typically would be admixed with acetic anhydride (typically 1to 5 moles of acetic anhydride to each mole of diacid) and the solutionheated to 80° C. to 100° C., for approximately 1 to 2 hours to providethe anhydride product. Alternatively, (as shown in Route A) thetricarboxylic acid monomer can be initially admixed with aceticanhydride (typically, there will be 1 to about 10 moles of aceticanhydride for each mole of triacid) and heated to 60° C. to about 120°C., preferably 80° C. to 100° C., for several hours to provide theanhydride product. The reactions to produce the anhydride arerepresentatively shown in the schematic below: ##STR5##

2. ACID-FUNCTIONAL POLYMERS

The polymerization of the novel monomers of this invention either aloneor with other unsaturated copolymerizable monomers, such as(meth)acrylic monomers or styrene, proceeds at excellent yield and canproduce polymers having excellent performance characteristics. Themonomers are practical for providing any desired acid value for thepolymer, which can then, if desired, be neutralized with a base such asammonia to provide water dispersibility and/or the pendent acid groupscan provide reactive sites for other materials having groups reactivewith acid groups such as epoxy, amine or hydroxyl groups.

The polymers which incorporate the monomers of this invention couldconveniently be prepared by polymerizing the styrene basedacid-functional monomer, and, normally, at least one othercopolymerizable monomer under free radical addition polymerizationconditions. Typically, the polymerization would be conducted in an inertsolvent and in the presence of an initiator, such as a peroxide or azocompound, at temperatures ranging from 35° C. to about 120° C., andespecially 75° C. to about 100° C. Representative initiators includedi-t-butyl peroxide, t-butyl peroctoate, cumene hydroperoxide, andazobis(isobutyronitrile).

The mixture of monomers used to prepare the polymers would typicallycomprise from 1 to about 100, and especially 5 to about 30, percent byweight of the styrene based tricarboxylic acid-functional monomer. Theremainder of the polymer would be comprised of at least one othermonomer copolymerizable with the styrene based acid-functional monomer.One preferred polymer is obtained from a mixture of monomers comprising5 to about 30 percent by weight of the unsaturated dicarboxylic acid,10% to about 40% of a copolymerizable hydroxy-functional monomer and 30%to about 85% of at least one other copolymerizable monomer.

Typically, the styrene based acid-functional monomers would becopolymerized with one or more monomers having ethylenic unsaturationand which are not reactive with the acid groups under the conditions ofpolymerization. Such monomers would include:

(i) acrylic, methacrylic, crotonic, tiglic, or other unsaturated acidsor derivatives thereof such as: acrylic acid, methacrylic acid, methylacrylate, ethyl acrylate, propyl acrylate, isopropyl acrylate, butylacrylate, isobutyl acrylate, ethylhexyl acrylate, amyl acrylate,3,5,5-trimethylhexyl acrylate, methyl methacrylate, ethyl methacrylate,propyl methacrylate, dimethylaminoethyl methacrylate, isobornylmethacrylate, ethyl tiglate, methyl crotonate, ethyl crotonate,2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate, 2-hydroxypropylacrylate, 4-hydroxybutyl methacrylate, 2-hydroxypropyl methacrylate,3-hydroxybutyl acrylate, 4-hydroxypentyl acrylate, 2-hydroxyethylethacrylate, 3-hydroxybutyl methacrylate, 2-hydroxyethyl chloroacrylate,diethylene glycol methacrylate, tetra ethylene glycol acrylate, etc.;

(ii) vinyl compounds such as vinyl acetate, vinyl propionate, vinylbutyrate, vinyl isobutyrate, vinyl benzoate, vinyl m-chlorobenzoate,vinyl p-methoxybenzoate, vinyl α-chloroacetate, vinyl toluene, vinylchloride, para vinyl benzyl alcohol, etc.;

(iii) styrene-based materials such as styrene, α-methyl styrene, α-ethylstyrene, α-bromo styrene, 2,6-dichlorostyrene, etc.;

(iv) allyl compounds such as allyl chloride, allyl acetate, allylbenzoate, allyl methacrylate, etc.;

(v) other copolymerizable unsaturated monomers such as ethylene,acrylonitrile, methacrylonitrile, dimethyl maleate, isopropenyl acetate,isopropenyl isobutyrate, acrylamide, methacrylamide, and dienes such as1,3-butadiene, etc.

The free radical addition polymers of this invention could typically beused as lacquers or as reactive polymers and would have application inadhesives, coatings, inks, plastics, chemical additives and fibers. Thependent acid functionality makes them especially useful as waterreducible polymers.

3. REACTIVE COATING COMPOSITIONS

If the acid-functional polymer contains other reactive functionality inaddition to acid functionality, such as hydroxyl groups, it could alsobe used with crosslinkers reactive with hydroxyl groups such as apolyisocyanate, or a nitrogen resin such as a condensate of an aldehydesuch as formaldehyde with a nitrogenous compound such as urea, melamineor benzoguanamine or a lower alkyl ether of such a condensate.

The novel acid-functional polymers of this invention could also becombined with compounds which are reactive with acid functionality toproduce reactive coating compositions. These reactive coatingcompositions could comprise:

(i) the acid-functional polymer and a polyepoxide;

(ii) the acid-functional polymer, a polyanhydride and a monoepoxide orpolyepoxide; or

(iii) the acid-functional polymer, a polyanhydride, a mono- orpolyepoxide, and a hydroxy-functional compound.

3.A. EPOXY-FUNCTIONAL COMPOUNDS

The preferred reactive compositions of this invention typically requirethe use of at least one epoxy-functional compound. The epoxy compound,preferably, will be a polyepoxide having an average of at least twoepoxy groups per molecule. If the acid-functional polymer of thisinvention is used in combination with an anhydride-functional compoundand, optionally a hydroxy-functional compound, then either a monoepoxideor a polyepoxide can be used.

Representative useful monoepoxides include the monoglycidyl ethers ofaliphatic or aromatic alcohols such as butyl glycidyl ether, octylglycidyl ether, nonyl glycidyl ether, decyl glycidyl ether, dodecylglycidyl ether, p-tert-butylphenyl glycidyl ether, and o-cresyl glycidylether. Monoepoxy esters such as the glycidyl ester of versatic acid(commercially available as CARDURA®E from Shell Chemical Company), orthe glycidyl esters of other acids such as tertiary-nonanoic acid,tertiary-decanoic acid, tertiary-undecanoic acid, etc. are also useful.Similarly, if desired, unsaturated monoepoxy esters such as glycidylacrylate, glycidyl methacrylate or glycidyl laurate could be used.Additionally, epoxidized oils having an average of one epoxy group permolecule could also be used as monoepoxides.

Other useful monoepoxies include styrene oxide, cyclohexene oxide,1,2-butene oxide, 2,3-butene oxide, 1,2-pentene oxide, 1,2-hepteneoxide, 1,2-octene oxide, 1,2-nonene oxide, 1,2-decene oxide, and thelike.

It is only necessary that the monoepoxide compounds have a sufficientlylow volatility to remain in the coating composition under the applicableconditions of cure.

Polyepoxides are especially preferred in the reactive coatings of thisinvention. Especially preferred as the poly-functional epoxy compounds,due to their reactivity and durability, are the polyepoxy-functionalcycloaliphatic epoxies. Preferably, the cycloaliphatic epoxies will havea number average molecular weight less than about 2,000 to minimize theviscosity. The cycloaliphatic epoxies are conveniently prepared bymethods well known in the art such as epoxidation of dienes or polyenes,or the epoxidation of unsaturated esters by reaction with a peracid suchas peracetic and/or performic acid.

Commercial examples of representative preferred cycloaliphatic epoxiesinclude 3,4-epoxycyclohexylmethyl 3,4-epoxy cyclohexane carboxylate(e.g. "ERL-4221" from Union Carbide Corp.);bis(3,4-epoxycyclohexylmethyl)adipate (e.g. "ERL-4299" from UnionCarbide Corporation); 3,4-epoxy-6-methylcyclohexylmethyl3,4-epoxy-6-methylcyclohexane carboxylate (e.g. "ERL-4201" from UnionCarbide Corp.); bis(3,4-epoxy-6-methylcyclohexylmethyl)adipate (e.g."ERL-4289" from Union Carbide Corp.); bis(2,3-epoxycyclopentyl) ether(e.g. "ERL-0400" from Union Carbide Corp.); dipentene dioxide (e.g."ERL-4269" from Union Carbide Corp.);2-(3,4-epoxycyclohexyl-5,5-spiro-3-4-epoxy) cyclohexane-metadioxane(e.g. "ERL-4234" from Union Carbide Corp.). Other commercially availablecycloaliphatic epoxies are available from Ciba-Geigy Corporation such asCY 192, a cycloaliphatic diglycidyl ester epoxy resin having an epoxyequivalent weight of about 154. The manufacture of representativeepoxies is taught in various patents including U.S. Pat. No. 2,750,395;2,884,408; 2,890,194; 3,027,357 and 3,318,822.

Other polyepoxides potentially useful in the practices of this inventioninclude aliphatic and aromatic polyepoxies, such as those prepared bythe reaction of an aliphatic polyol or polyhydric phenol and anepihalohydrin. Other useful epoxies include epoxidized oils andepoxy-functional copolymers such as acrylic polymers derived fromethylenically unsaturated epoxy-functional monomers such as glycidylacrylate or glycidyl methacrylate in combination with othercopolymerizable monomers such as the (meth)acrylic and other unsaturatedmonomers. Representative useful (meth)acrylic monomers include methylacrylate, ethyl acrylate, propyl acrylate, isopropyl acrylate, butylacrylate, isobutyl acrylate, ethyl hexyl acrylate, amyl acrylate,3,5,5-trimethylhexyl acrylate, methyl methacrylate, lauryl methacrylate,butyl methacrylate, 2-hydroxyethyl methacrylate, acrylonitrile,methacrylonitrile, acrylamide and methacrylamide. Other copolymerizablemonomers include vinyl acetate, vinyl propionate, vinyl butyrate, vinylisobutyrate, vinyl benzoate, vinyl m-chlorobenzoate, vinyl p-methoxybenzoate, vinyl chloride, styrene, α-methyl styrene, diethyl fumarate,dimethyl maleate, etc. Monomers having acid functionality, or otherfunctionality reactive with epoxide groups should normally not beutilized in the manufacture of the polyepoxide vehicle.

The ratio of acid groups to epoxy groups can be widely varied to giveany desired level of crosslinking within the practice of this invention.When the reactive coating system comprises just the acid-functionalpolymer and a polyepoxide, at least 0.1 acid groups should be presentfor each epoxy group. It is generally preferred, however, to provideabout 0.1 to about 2.0 acid groups for each epoxy group in such areactive system, and especially preferred to provide about 0.3 to about1.0 acid groups for each epoxy group in such a system.

It is especially preferred in the practice of this invention to includea catalyst for the reaction of epoxy and acid groups. Tertiary amines,secondary amines such as ethyl imidazole, quaternary ammonium salts, andnucleophilic catalysts such as lithium iodide, phosphonium salts, andphosphines such as triphenyl phosphine are especially useful ascatalysts for epoxy/acid reactions. The catalyst for the epoxy/acidreaction will typically be present at a level of at least 0.01% byweight of the total acid-functional polymer and epoxy-functionalcompound and will preferably be present at about 0.1 to about 3.0%.

3.B. ANHYDRIDE FUNCTIONAL COMPOUNDS

Useful reactive coating compositions incorporating the acid-functionalpolymer of this invention and an epoxy-functional compound may,optionally, also incorporate an anhydridefunctional compound to altervarious performance properties of the final coating. Theanhydride-functional compounds which are useful in the practice of thisinvention can be any aliphatic or aromatic compound having at least twocyclic carboxylic acid anhydride groups in the molecule. Polymericanhydrides having number average molecular weights between 500 and 7,000are most useful. Especially preferred in the practice of this inventionis the use of acrylic polymers having anhydride functionality. These areconveniently prepared as is well known in the art by the polymerizationunder free radical addition polymerization conditions of at least oneunsaturated monomer having anhydride functionality, such as maleicanhydride, citraconic anhydride, itaconic anhydride, propenyl succinicanhydride, etc. optionally with other ethylenically unsaturated monomerssuch as the esters of unsaturated acids, vinyl compounds, styrene-basedmaterials, allyl compounds and other copolymerizable monomers, all asrepresentatively taught elsewhere in this specification.

The monomers which are copolymerized with the unsaturated anhydridemonomer should, of course, be free of any functionality which couldreact with the anhydride group during the polymerization. Theseanhydride-functional polymers can be conveniently prepared byconventional free radical addition polymerization techniques. Typicallythe polymerization will be conducted in an inert solvent and in thepresence of an initiator at temperatures ranging from 35° C. to about200° C. The anhydride-functional free radical addition polymers shouldtypically comprise at least 5% by weight of the anhydride. An especiallypreferred anhydride-functional polymer comprises the free radicaladdition polymerization product of

(a) 5 to 40, and especially 15 to about 25, weight percent of anethylenically unsaturated monoanhydride and

(b) 60 to 95, and especially 75 to about 85, weight percent of at leastone other ethylenically unsaturated monomer copolymerizable with theethylenically unsaturated anhydride.

Other polyanhydrides can also be optionally utilized in the practice ofthis invention. Ester anhydrides can be prepared, as is known in theart, by the reaction of e.g. trimellitic anhydride with polyols. Otherrepresentative, suitable polyanhydrides include poly-functional cyclicdianhydrides such as cyclopentane tetracarboxylic acid dianhydride,diphenyl-ether tetracarboxylic acid dianhydride, 1,2,3,4,-butanetetracarboxylic acid dianhydride, and the benzophenone tetracarboxylicdianhydrides such as 3,3',4,4'-benzophenone tetracarboxylic dianhydride,and 2,bromo-3,3',4,4'-benzophenone tetracarboxylic acid dianhydride.Trianhydrides such as the benzene and cyclohexene hexacarboxylic acidtrianhydrides are also useful. Additionally, useful polyanhydrides canbe prepared by the maleinization of polyunsaturated compounds such asunsaturated rubbers, unsaturated oils and unsaturated hydrocarbons.

Although it is not our intent to be bound by theory, it is believed thatin the course of the curing reaction of the components of thisinvention, that at least some of the acid groups and epoxy groups reactto produce ester groups and hydroxyl groups and that at least some ofthese hydroxyl groups are reacted with the anhydride groups to produceester groups and additional acid groups. It is, therefore, especiallypreferred in the practice of this invention to include a catalyst forthe reaction of anhydride groups and hydroxyl groups and also a catalystfor the reaction of epoxy and acid groups.

When the reactive coating composition incorporates apolyanhydride-functional compound along with the acid-functional polymerand the epoxy-functional compound, the ratios of anhydride to acid toepoxy groups can be widely varied to give any desired level ofcrosslinking within the practice of this invention. Typically, thepolyanhydride should be present in an amount to provide at least about0.01 anhydride groups for each epoxy group in the reactive coating. Itis preferred, however, to provide about 0.3 to about 6.0 acid groups andabout 0.6 to about 12.0 epoxy groups for each anhydride group in thereactive system. An especially preferred formulation range provides 2.0to about 5.0 acid groups and 3.0 to about 8.0 epoxy groups for eachanhydride group.

3.C. HYDROXY-FUNCTIONAL COMPOUNDS

If desired, the reactive coating compositions of this invention whichcomprise the acid-functional polymer, the epoxy-functional compound andthe anhydride-functional compound can also incorporate ahydroxy-functional compound. The hydroxy-functional compounds which areuseful in the practice of this invention have an average of at least twohydroxyl groups per molecule. Although low molecular weight diols andpolyols such as propylene glycol, 1,6-hexanediol, triethanol amine, andpentaerythritol can be utilized in the practice of this invention, it isespecially preferred to utilize polymeric hydroxy-functional compoundssuch as polyethers, polyesters, acrylics, polyurethanes,polycaprolactones, etc.

Preferably the hydroxy-functional polymer will have a number averagemolecular weight of at least about 400. Typical number average molecularweights will range from about 400 to about 30,000, and especially 1,000to about 15,000. In order to provide the fastest rate of reaction duringcure it is preferred in the practice of this invention to utilizehydroxy-functional compounds having predominantly, and preferably all,primary hydroxyl functionality.

Representative hydroxy-functional polymers include those described inSections 3.C.1 through 3.C.5 below:

3.C.1. Polyether polyols are well known in the art and are convenientlyprepared by the reaction of a diol or polyol with the correspondingalkylene oxide. These materials are commercially available and may beprepared by a known process such as, for example, the processesdescribed in Encyclopedia of Chemical Technology, Volume 7, pages257-262, published by Interscience Publishers, Inc., 1951; and inKirk-Othmer Encyclopedia of Chemical Technology, Volume 18, pages638-641, published by Wiley-International, 1982. Representative examplesinclude the polypropylene ether glycols and polyethylene ether glycolssuch as those marketed as Niax® Polyols from Union Carbide Corporation.

3.C.2. Another useful class of hydroxy-functional polymers are thoseprepared by condensation polymerization reaction techniques as are wellknown in the art. Representative condensation polymerization reactionsinclude polyesters prepared by the condensation of polyhydric alcoholsand polycarboxylic acids or anhydrides, with or without the inclusion ofdrying oil, semi-drying oil, or non-drying oil fatty acids. By adjustingthe stoichiometry of the alcohols and the acids while maintaining anexcess of hydroxyl groups, hydroxy-functional polyesters can be readilyproduced to provide a wide range of desired molecular weights andperformance characteristics.

The polyester polyols are derived from one or more aromatic and/oraliphatic polycarboxylic acids, the anhydrides thereof, and one or morealiphatic and/or aromatic polyols. The carboxylic acids include thesaturated and unsaturated polycarboxylic acids and the derivativesthereof, such as maleic acid, fumaric acid, succinic acid, adipic acid,azelaic acid, and dicyclopentadiene dicarboxylic acid. The carboxylicacids also include the aromatic polycarboxylic acids, such as phthalicacid, isophthalic acid, terephthalic acid, etc. Anhydrides such asmaleic anhydride, phthalic anhydride, trimellitic anhydride, or NadicMethyl Anhydride (brand name formethylbicyclo[2.2.1]heptene-2,3-dicarboxylic anhydride isomers) can alsobe used.

Representative saturated and unsaturated polyols which can be reactedwith the carboxylic acids to produce hydroxy-functional polyestersinclude diols such as ethylene glycol, dipropylene glycol,2,2,4-trimethyl 1,3-pentanediol, neopentyl glycol, 1,2-propanediol,1,4-butanediol, 1,3-butanediol, 2,3-butanediol, 1,5-pentanediol,1,6-hexanediol, 2,2-dimethyl-1, 3-propanediol,1,4-cyclohexanedimethanol, 1,2-cyclohexanedimethanol,1,3-cyclohexanedimethanol, 1,4-bis(2-hydroxyethoxy)cyclohexane,trimethylene glycol, tetramethylene glycol, pentamethylene glycol,hexamethylene glycol, decamethylene glycol, diethylene glycol,triethylene glycol, tetraethylene glycol, norbornylene glycol,1,4-benzenedimethanol, 1,4-benzenediethanol,2,4-dimethyl-2-ethylenehexane-1,3-diol, 2-butene-1,4-diol, and polyolssuch as trimethylolethane, trimethylolpropane, trimethylolhexane,triethylolpropane, 1,2,4-butanetriol, glycerol, pentaerythritol,dipentaerythritol, etc.

Typically, the reaction between the polyols and the polycarboxylic acidsis conducted at about 120° C. to about 200° C. in the presence of anesterification catalyst such as dibutyl tin oxide.

3.C.3. Additionally, hydroxy-functional polymers can be prepared by thering opening reaction of epoxides and/or polyepoxides with primary or,preferably, secondary amines or polyamines to produce hydroxy-functionalpolymers. Representative amines and polyamines include ethanol amine,N-methylethanol amine, dimethyl amine, ethylene diamine, isophoronediamine, etc. Representative polyepoxides include those prepared bycondensing a polyhydric alcohol or polyhydric phenol with anepihalohydrin, such as epichlorohydrin, usually under alkalineconditions. Some of these condensation products are availablecommercially under the designations EPON or DRH from Shell ChemicalCompany, and methods of preparation are representatively taught in U.S.Pat. Nos. 2,592,560; 2,582,985 and 2,694,694.

3.C.4. Other useful hydroxy-functional polymers can be prepared by thereaction of at least one polyol, such as those representativelydescribed in Section 3.C.2 above, with polyisocyanates to producehydroxy-functional urethanes. Representative polyisocyanates having twoor more isocyanate groups per molecule include the aliphatic compoundssuch as ethylene, trimethylene, tetramethylene, pentamethylene,hexamethylene, 1,2-propylene, 1,2-butylene, 2,3-butylene, 1,3-butylene,ethylidene and butylidene diisocyanates; the cycloalkylene compoundsstich as 3-isocyanatomethyl-3,5,5-trimethylcyclohexylisocyanate, and the1,3-cyclopentane, 1,3-cyclohexane, and 1,2-cyclohexane diisocyanates;the aromatic compounds such as m-phenylene, p-phenylene, 4,4'-diphenyl,1,5-naphthalene and 1,4-naphthalene diisocyanates; thealiphatic-aromatic compounds such as 4,4'-diphenylene methane, 2,4- or2,6-toluene, or mixtures thereof, 4,4'-toluidine, and 1,4-xylylenediisocyanates; the nuclear substituted aromatic compounds such asdianisidine diisocyanate, 4,4'-diphenylether diisocyanate andchlorodiphenylene diisocyanate; the triisocyanates such as triphenylmethane-4,4',4"-triisocyanate, 1,3,5-triisocyanate benzene and2,4,6-triisocyanate toluene; and the tetraisocyanates such as4,4'-diphenyl-dimethyl methane-2,2'-5,5'-tetraisocyanate; thepolymerized polyisocyanates such as tolylene diisocyanate dimers andtrimers, and other various polyisocyanates containing biuret, urethane,and/or allophanate linkages. The polyisocyanates and the polyols aretypically reacted at temperatures of 25° C. to about 150° C. to form thehydroxy-functional polymers.

3.C.5. Useful hydroxy-functional polymers can also be convenientlyprepared by free radical polymerization techniques such as in theproduction of acrylic resins. The polymers are typically prepared by theaddition polymerization of one or more monomers. At least one of themonomers will contain, or can be reacted to produce, a reactive hydroxylgroup. Representative hydroxy-functional monomers include 2-hydroxyethylacrylate, 2-hydroxypropyl acrylate, 4-hydroxybutyl methacrylate,2-hydroxypropyl methacrylate, 3-hydroxybutyl acrylate, 4-hydroxypentylacrylate, 2-hydroxyethyl ethacrylate, 3-hydroxybutyl methacrylate,2-hydroxyethyl chloroacrylate, diethylene glycol methacrylate,tetraethylene glycol acrylate, para-vinyl benzyl alcohol, etc. Typicallythe hydroxy-functional monomers would be copolymerized with one or moremonomers having ethylenic unsaturation such as thenon-hydroxy-functional monomers included in Section 2 above.

The acrylics are conveniently prepared by conventional free radicaladdition polymerization techniques. Frequently, the polymerization willbe catalyzed by conventional initiators known in the art to generate afree radical such as azobis(isobutyronitrile), cumene hydroperoxide,t-butyl perbenzoate, etc. Typically, the unsaturated monomers are heatedin the presence of the free radical initiator at temperatures rangingfrom about 35° C. to about 200° C., and especially 100° C. to 160° C.,to effect the polymerization. The molecular weight of the polymer can becontrolled, if desired, by the monomer selection, reaction temperatureand time, and/or the use of chain transfer agents as is well known inthe art.

Especially preferred in the practice of this invention arehydroxy-functional polyesters and hydroxy-functional acrylic polymers.An especially preferred hydroxy-functional polymer is the additionpolymerization reaction product of

(a) 10 to about 40 weight percent of a hydroxy-functional ethylenicallyunsaturated monomer and

(b) 60 to about 90 weight percent of at least one ethylenicallyunsaturated monomer copolymerizable with the hydroxy-functional monomer.

When the reactive coating system incorporates a hydroxy-functionalcompound along with the acid-functional polymer, the epoxy-functionalcompound, and polyanhydride compound, the relative levels of each ofthese reactive groups may also be widely varied within the practice ofthis invention. It is preferred, however, to provide about 0.05 to about3.0 acid groups and about 0.5 to about 4.0 epoxy groups and about 0.5 toabout 6.0 hydroxyl groups for each anhydride group in the reactivesystem. An especially preferred formulation range provides 1.0 to about2.0 acid groups and 1.0 to about 3.0 epoxy groups and about 1.0 to about4.0 hydroxyl groups for each anhydride group.

It is especially preferred in the practice of this invention when usinganhydride-functional compounds in combination with the acid-functionalpolymers and epoxy-functional compounds to include a catalyst for thereaction of the epoxy and acid groups and a catalyst for the reaction ofanhydride groups and hydroxyl groups as taught in this specification. Itis especially preferred in the practice of this invention to utilizetertiary amines and especially N-methylimidazole as a catalyst for theanhydride/hydroxyl reaction. The catalyst for the anhydride/hydroxylreaction will typically be present at a level of at least 0.01% byweight of the anhydride compound and preferably 1.0 to about 5.0%.

If desired, more than one of any of the acid-functional,anhydride-functional, epoxy-functional or hydroxy-functional compoundscould be utilized in a single curable coating formulation.

The coatings of this invention can be cured at temperatures ranging fromabout room temperature up to about 350° F. The coatings can be used asclear coatings and/or they may contain pigments as is well known in theart. Representative opacifying pigments include white pigments such astitanium dioxide, zinc oxide, antimony oxide, etc. and organic orinorganic chromatic pigments such as iron oxide, carbon black,phthalocyanine blue, etc. The coatings may also contain extenderpigments such as calcium carbonate, clay, silica, talc, etc.

The coatings may also contain other additives such as flow agents,catalysts, diluents, solvents, ultraviolet light absorbers, etc.

Since the curable compositions of this invention are typically providedas multi-package systems which must be mixed together prior to use, thepigments, catalysts and other additives can be conveniently added to anyor all of the individual packages.

The coatings of this invention may typically be applied to any substratesuch metal, plastic, wood, glass, synthetic fibers, etc. by brushing,dipping, roll coating, flow coating, spraying or other methodconventionally employed in the coating industry.

One preferred application of the curable coatings of this inventionrelates to their use as clearcoats and/or basecoats inclearcoat/basecoat formulations.

Clearcoat/basecoat systems are well known, especially in the automobileindustry where it is especially useful to apply a pigmented basecoat,which may contain metallic pigments, to a substrate and allow it to forma polymer film followed by the application of a clearcoat which will notmix with or have any appreciable solvent attack upon the previouslyapplied basecoat. The basecoat composition may be any of the polymersknown to be useful in coating compositions including the reactivecompositions of this invention.

One useful polymer basecoat includes the acrylic addition polymers,particularly polymers or copolymers of one or more alkyl esters ofacrylic acid or methacrylic acid, optionally together with one or moreother ethylenically unsaturated monomers. These polymers may be ofeither the thermoplastic type or the thermosetting, crosslinking typewhich contain hydroxyl or amine or other reactive functionality whichcan be crosslinked. Suitable acrylic esters and unsaturated monomers foreither type of polymer include methyl methacrylate, ethyl methacrylate,propyl methacrylate, butyl methacrylate, ethyl acrylate, butyl acrylate,vinyl acetate, acrylonitrile, acrylamide, styrene, vinyl chloride, etc.Where the polymers are required to be of the crosslinking type, suitablefunctional monomers which can be used in addition to those alreadymentioned include acrylic or methacrylic acid, hydroxy ethyl acrylate,2-hydroxy propyl methacrylate, glycidyl acrylate, tertiary-butyl aminoethyl methacrylate, etc. The basecoat composition may, in such a case,also contain a crosslinking agent such as a polyisocyanate, apolyepoxide, or a nitrogen resin such as a condensate of an aldehydesuch as formaldehyde with a nitrogenous compound such as urea, melamineor benzoguanamine or a lower alkyl ether of such a condensate. Otherpolymers useful in the basecoat composition include vinyl copolymerssuch as copolymers of vinyl esters of inorganic or organic acids, suchas vinyl chloride, vinyl acetate, vinyl propionate, etc., whichcopolymers may optionally be partially hydrolyzed so as to introducevinyl alcohol units.

Other polymers useful in the manufacture of the basecoat include alkydresins or polyesters which can be prepared in a known manner by thecondensation of polyhydric alcohols and polycarboxylic acids, with orwithout the inclusion of natural drying oil fatty acids as describedelsewhere in this specification. The polyesters or alkyds may contain aproportion of free hydroxyl and/or carboxyl groups which are availablefor reaction, if desired with suitable crosslinking agents as discussedabove.

If desired, the basecoat composition may also contain minor amounts of acellulose ester, to alter the drying or viscosity characteristics of thebasecoat.

Typically, the basecoat will include pigments conventionally used forcoating compositions and after being applied to a substrate, which mayor may not previously have been primed, the basecoat will be allowedsufficient time to form a polymer film which will not be lifted duringthe application of the clearcoat. The basecoat may be heated or merelyallowed to air-dry to form the film. Generally, the basecoat will beallowed to dry for about 1 to 20 minutes before application of theclearcoat. The clearcoat is then applied to the surface of the basecoat,and the system can be allowed to dry at room temperature or, if desired,can be force dried by baking the coated substrate at temperaturestypically ranging up to about 350° F.

Typically, the clearcoat may contain ultraviolet light absorbers such ashindered phenols or hindered amines at a level ranging up to about 6% byweight of the vehicle solids as is well known in the art. The clearcoatcan be applied by any application method known in the art, butpreferably will be spray applied. If desired, multiple layers ofbasecoat and/or clearcoat can be applied. Typically, both the basecoatand the clearcoat will each be applied to give a dry film thickness ofabout 0.01 to about 6, and especially about 0.5 to about 3.0 mils.

If desired, the novel reactive compositions taught herein could be usedas a basecoat, in which case the clearcoat could also comprise the novelreactive coatings taught herein, or other polymers, including thepolymers taught herein as being useful as basecoat formulations could beutilized as clearcoats.

The following examples have been selected to illustrate specificembodiments and practices of advantage to a more complete understandingof the invention. Unless otherwise stated, "parts" means pans-by-weightand "percent" is percent-by-weight. The starting raw materials utilizedin these examples are commercially available. The vinyl benzyl chlorideis a 70/30 meta/para isomer commercially available from Dow ChemicalCompany. The sodium metal, diethylmalonate, ethyl chloroacetate, aceticanhydride, butylated hydroxy toluene, and, unless otherwise indicated,the triethyl-1,1,2-ethanetricarboxylate, were obtained from AldrichChemical Company. The absolute ethanol was obtained from USI-QuantumChemical Company.

EXAMPLE A Triethyl-1,1,2-Ethane Tricarboxylate

A solution of sodium ethoxide in ethanol was prepared by slowly adding559.4 g sodium metal into 7890 g of absolute ethanol. Next, 3891.9 g ofdiethyl malonate was added to the ethanol solution over 45 minutes at aninitial temperature of 25 ° C. The mixture was homogenized by heating at50° C. for 40 minutes. Next, 3000 g ethyl chloroacetate was slowly addedover approximately 90 minutes, while the reaction mixture was maintainedat 40°-50° C. with occasional warming. The mixture was then heated atreflux for 2 hours, then cooled to room temperature.

The mixture was worked-up by stripping off approximately two-thirds ofthe ethanol (˜750-800 ml). The residue was then washed with water andextracted with toluene. The toluene solution was dried over magnesiumsulfate, followed by removal of the toluene to give a dark red residue.The product residue was distilled under reduced pressure to give 3252 g(approximately 54.3% yield) of triethyl-1,1,2-ethane tricarboxylate in˜97% purity.

EXAMPLE B Triethyl 1-(3/4-Vinyl Benzyl)-1,1,2-Ethane Tricarboxylate

An ethanol solution of sodium ethoxide was prepared by adding 283 g ofsodium metal over 8 hours to 6404 g of ethanol (maximum temperature 60°C.). Triethyl-1,1,2-ethane tricarboxylate (Example A, 3156.9 g) was thenadded over 20 minutes to the ethanol solution (maximum temperature 30°C.). The mixture was then heated at reflux for 5-10 minutes, then cooledto 25° C. Next, 1816.3 g of vinyl benzyl chloride was added over 40minutes, while keeping the temperature under 35° C. A small amount ofbutylated hydroxy toluene inhibitor was added. The mixture was heated atreflux for 2 hours and 20 minutes and then allowed to cool to roomtemperature.

The reaction mixture was neutralized (pH ˜7) with glacial acetic acid,and approximately two-thirds of the ethanol was stripped off underreduced pressure. Sodium chloride was filtered off. The unpurifiedstyryl methylene triester/ethanol solution (63.6% NVM in ethanol) wasthen utilized to produce the corresponding tricarboxylic acid as shownin Example E.

EXAMPLE C Triethyl 1-(3/4-Vinyl Benzyl)-1,1,2-Ethane Tricarboxylate

A sodium ethoxide/ethanol solution was prepared by slowly adding 16.02 gof sodium metal to 365 g of absolute ethanol with slow stirring. Themixture was then heated at reflux for 5-10 minutes.Triethyl-1,1,2-ethane tricarboxylate (180 g from Aldrich ChemicalCompany) was added over 20 minutes to the mixture at room temperature.The mixture was heated at reflux for 5-10 minutes, then cooled to 25° C.Next, 112.9 g of vinyl benzyl chloride was added over 20 minutes(maximum temperature of the reaction mixture was 45 ° C.). A smallamount of butylated hydroxy toluene inhibitor was added. The mixture washeated to reflux for 2 hours, then cooled to room temperature.

The reaction mixture was neutralized (pH ˜7) with glacial acetic acid.About two-thirds of the ethanol was stripped off under reduced pressure.Six hundred sixty-five milliliters of deionized water was added and theproduct was extracted with toluene. The combined toluene extracts weredried over sodium sulfate. Removing the volatiles with rotaryevaporation produced 255.2 g of triethyl-1-(3/4-vinylbenzyl)-1,1,2-ethane tricarboxylate as a yellow liquid in an isolatedyield of 96% of theory. NMR and infrared spectral data confirmed thestructure of the tricarboxylate product.

EXAMPLE D 1-(3/4-Vinyl Benzyl)-1,1,2-Ethane Tricarboxylic Acid

An aqueous/ethanolic potassium hydroxide solution was prepared by slowlymixing 2805 ml of absolute ethanol and 147.5 ml of deionized water. Asmall amount of butylated hydroxy toluene inhibitor was added. Potassiumhydroxide (363 g) was added slowly keeping the temperature below reflux.The mixture was then cooled to 30° C. and, 240 g, (approximately 0.662mol) of the crude product of the vinyl benzyl triester of Example C wasquickly added. The mixture rapidly turned cloudy and then becamehomogeneous upon heating to reflux. An additional small amount ofbutylated hydroxy toluene inhibitor was again added and reflux wascontinued for 4 hours. The precipitate laden mixture was then allowed tocool to room temperature. The tricarboxylate salt was collected bysuction filtration, then dissolved in deionized water (800 ml) andneutralized with dilute aqueous hydrochloric acid (5:1 cone. HCl/H₂ Ovol. ratio) to a pH <2. Two additions of approximately 3000 ml each ofanhydrous acetone was added to the acidified solution and the potassiumchloride precipitate was filtered off. The acetone was then stripped offand the process was then repeated. The remaining volatiles were thenremoved under reduced pressure to give an isolated yield of 113.1 g(74.4%) of an off white solid (mp 112.5°-125° C. decomposed). NMR,infrared and acid dissociation constants data were used to characterizethe tricarboxylic acid product. In water, aqueous potassium hydroxidetitration identified the Pka's of the three carboxylic acid groups as2.60; 4.59 and 8.06.

EXAMPLE E 1-(3/4-Vinyl Benzyl)-1,1,2-Ethane Tricarboxylic Acid

An aqueous potassium hydroxide solution (6126 g, 109.2 mol of potassiumhydroxide in 2490 g of water) was slowly added to 6375 g (11.17 mol) ofthe unpurified vinyl benzyl triester/ethanol solution of Example B,(36.47% NVM) containing a small amount of butylated hydroxy tolueneinhibitor, while keeping the exothermic reaction below reflux. Anadditional small amount of butylated hydroxy toluene was again added.The mixture was then heated to reflux for 4 hours, and cooled to roomtemperature. The precipitated solid tricarboxylate salt was collected byfiltration. Additional ethanol (12000 g) and then propanol (12000 g)were used to precipitate out the remaining salt which was collected byfiltration.

A dispersion of the tricarboxylate salt was made in anhydrous acetone.The salt was neutralized by acidifying the mixture with a concentratedhydrochloric acid (HCl)/water solution (5:1 volume ratio) to a pH of <2.The acetone, aqueous HCl solution was then treated with a 2:1hexane/toluene mixture. Stripping volatiles from the residual solutionyielded 2777 g of an orange solid crude product. NMR and infraredspectral data confirmed the structure as the desired tricarboxylate. Theproduct also contained some neutralized potassium carboxylate salt.

One potential utility of the acid monomers of this invention is theiruse as polymerizable components of free radical addition polymers.Theoretical productions of such polymers are given in Examples F and G.

EXAMPLE F HYDROXY-FUNCTIONAL COPOLYMER

A representative hydroxy-functional polymer incorporating the styrenebased acid-functional monomer of this invention could be prepared, in arepresentative fashion, as follows:

A reaction vessel equipped with a mechanical stirrer, water cooledcondenser, nitrogen inlet, water trap, thermometer and heating mantelcould be charged with 172.5 parts of n-butyl acetate and heated toapproximately 200° F. and a monomer premix comprising 91.2 parts ofmethyl methacrylate, 58 parts of butyl acrylate, 58 parts of hydroxyethyl methacrylate, 25 parts of the monomer of Example D, 54 partsstyrene and an initiator premixture composed of 11.5 parts of n-butylacetate and 5.7 parts of 2,2'-azobis(2-methylbutyronltrile) could bemetered simultaneously into the polymerization reactor at a constantrate for approximately 4 hours. The reaction temperature could bemaintained for an additional 2 hours after the addition was completedand then allowed to cool to yield the hydroxy-functional acrylic polymerincorporating the styrene based tricarboxylic acid of this invention.Such a hydroxy-functional polymer could be neutralized with a base suchas ammonia to provide water dispersibility and could be utilized in anaqueous coating composition in combination with a typical crosslinkingagent, such as a melamine curing agent or a blocked isocyanate toprovide curable, water reducible coating compositions.

Another potential utility for the acid-functional monomers of thisinvention is as precursors for the production of dicarboxylic anhydridemonomers. These anhydride monomers have special utility due to their lowtemperature reactivity with hydroxyl groups and their convenientpolymerization through they unsaturation to produce anhydride-functionalpolymers. The production of such an anhydride monomer is shown inExample H.

EXAMPLE G Acid-Functional Polymer

An acid-functional polymer could be prepared, in a representativefashion, as follows:

A reaction vessel equipped as described in Example F could be chargedwith 170.0 parts of n-butyl acetate and heated to approximately 200° F.and a monomer premix comprising, representatively, 80.0 parts methylmethacrylate, 60 parts butyl acrylate, 95 parts of the monomer ofExample C., 50 parts styrene and an initiator premixture composed of11.0 parts of n-butyl acetate and 6.0 parts of2,2'-azobis(2-methylbutyronitrile) could be metered simultaneously intothe polymerization reactor at a constant rate for several hours. Thereaction temperature would be maintained for several hours after theaddition was completed to yield the acrylic polymer incorporating thedicarboxylic acid of this invention. Such an acid-functional polymercould be utilized in combination with a polyepoxide, such as ERL-4299 toproduce a curable composition. Another utility of the acid-functionalmonomers of this invention is the production of anhydride-functionalmonomers. A representative preparation is shown in Example H.

EXAMPLE H 2-(3/4-Vinyl Benzyl) Succinic Anhydride

A mixture of 5 g (0.018 mol) of the vinyl benzyl triacid of Example E,10 g (0.098 mol) of acetic anhydride and a small amount of butylatedhydroxy toluene inhibitor was prepared. Gas evolution began at roomtemperature and the mixture was heated to a temperature of 100°-103° C.in a paraffin wax bath and maintained at that temperature for 2-2.5hours after which, the reaction mixture was allowed to cool to roomtemperature. Volatiles were stripped from the mixture providing 2.72 g(63.4% yield) of a brown viscous oil which was confirmed by infrared andNMR analyses as the desired 2-(3/4-vinyl benzyl) succinic anhydride.

While this invention has been described by a specific number ofembodiments, other variations and modifications may be made withoutdeparting from the spirit and scope of the invention as set forth in theappended claims. The entire disclosure of all applications, patents andpublications cited herein are hereby incorporated by reference.

The invention claimed is:
 1. An unsaturated acid-functional monomerhaving the structure: ##STR6## wherein R¹ is hydrogen or methyl and Z isa direct bond or is a divalent radical having 1 to about 20 carbonatoms.
 2. The monomer of claim 1 wherein R¹ is hydrogen.
 3. The monomerof claim 1 wherein R¹ is methyl.
 4. The monomer of claim 2 wherein Z isa direct bond.
 5. The monomer of claim 3 wherein Z is a direct bond. 6.The monomer of claim 1 wherein Z is a divalent polymethylene chain--(--CH₂ --)_(n) --wherein n is 1 to 20.